What are you planning? Building a ground loop into your garden will be
the only way to put that power into the antenna. At VLF and your E field
antenna, you would have to deal with several 10 kV if you actually want
to run > 1 kW. However on a ground loop, the amplifier will be the
limiting factor :-)
How much space to you have between the electrodes? All you will need is
a series C to resonate the antenna.
Use a big ferrite transformer to match the output impedance to the
antenna impedance.
Always use a series C on the primary side of the transformer, if bridged
or not, to avoid any damage due to an eventual DC-component.

Use a big ferrite core with just enough primary turns as necessary.
Now its time for Andy to post the formula again.
73, Stefan
Am 14.04.2019 15:37, schrieb Chris Wilson:

Hello LF'ers
Having collected my audio amp from Paul Nicholson (VERY many thanks
Paul, it's an awesome looking beast.... :)) I would appreciate anyone
else getting one posting their thoughts and results matching the input
and output for VLF usage. Both for antenna and ground comms usage.
Thanks.